This invention generally relates to systems and methods for processing blood and other biological fluids.
FIG. 1 shows a typical disposable bag set used in the prior art to collect platelets from whole blood. The set includes a needle 10 or cannula, which is inserted into a vein of a donor. The needle 10 is connected to the tube 11, which in turn is connected to collection bag 12, so as to allow whole blood to flow from the donor through the needle 10 and the tube 11 into collection bag 12. The collection bag 12 contains anticoagulant. After the desired amount of blood has been collected into collection bag 12, the needle 10 is removed from the donor, and tube 11 is cut and heat sealed. The remainder of the bag set is then brought to a centrifuge, which spins the bag set so that the blood in collection bag 12 separates into platelet-rich plasma and red blood cells. Typically, the centrifuge is not located at the point where the blood donation takes place.
After the blood has separated into platelet-rich plasma and red blood cells (RBCs), the bag set is removed from the centrifuge. The platelet-rich plasma is urged from collection bag 12 through tube 13 into platelet-storage bag 14. The tube 13 leading to the platelet- and plasma-storage bags 14, 15 is then cut and heat sealed. Storage-solution bag 16 holds RBC-storage solution. After the platelet-rich plasma has been urged into the platelet-storage bag 14, the RBC-storage solution is urged from the storage-solution bag 16 into the collection bag 12. The tube 41 connecting the collection and storage-solution bags 12, 16 is then cut and heat sealed.
At this stage, the bag set has been divided into two portions: (i) the first portion consists of the collection bag 12, which now holds primarily red blood cells (along with storage solution), filter 17, RBC-storage bag 18, and the tubing 19 that connects these components, and (ii) the second portion consists of the platelet-storage bag 14, which now holds platelet-rich plasma, and the plasma-storage bag 15 and the tubing that connects these two components.
The first portion may be hung, so that gravity causes the RBC component to pass from the collection bag 12 through the filter 17 to RBC-storage bag 18. The filter 17 removes white blood cells (WBCs) from the red blood cells. After the red blood cells (and storage solution) pass into the RBC-storage bag 18, tube 19 is cut and heat sealed.
To collect platelets, the second portion is centrifuged at a high rotational speed in order to separate the platelets from the plasma. After the platelets have been separated from the plasma, some of the plasma is urged from the platelet-storage bag 14 into the plasma-storage bag 15. Typically, 50 mls of plasma are left with the platelets in the platelet-storage bag 14. After the desired amount of plasma has been removed from the platelet-storage bag 14 to the plasma-storage bag 15, the tube connecting these two bags is cut and heat sealed. Thus, at the end of the procedure, the platelet-storage bag 14 holds platelets in about 50 ml of plasma, the plasma-storage bag 15 holds platelet-poor plasma, and the RBC-storage bag 18, of course, holds red blood cells.
This prior-art process of collecting and separating blood components involves many steps and frequent human intervention. The arrangement of the prior-art bag set does not permit the process to be easily automated.
The present invention is directed to systems and methods for collecting, from whole blood, platelets suspended in plasma. By centrifuging the blood at a high enough rotational speed, the platelets are separated from the plasma and the red blood cells. In a preferred embodiment, some of the plasma is removed while the centrifuge is being spun to keep the platelets separated from the plasma. Then, the speed of rotation is altered so as to cause the platelets to mix with the remaining plasma. The platelets can then be collected with the remaining plasma.
A system that may be used for carrying out the invention includes a centrifuge rotor, a flow-control arrangement and a spinner. The flow-control arrangement introduces whole blood into the centrifuge rotor and removes blood components from the centrifuge rotor. A controller causes the spinner to rotate at two different speeds: The rotor is spun at a first speed so as to separate the blood into a first component, a second component and a third component. The first component is primarily plasma. The second component is located, while the rotor is being spun, outside of the first component and is primarily red blood cells. The third component is located, while the rotor is being spun, between the first and second components and includes platelets. The controller causes the rotor""s speed of rotation to be altered so as to cause the third component to mix with the first component. The controller also causes the flow-control arrangement to remove from the rotor a portion of the plasma containing platelets.
As noted above, in a preferred embodiment, the controller causes the flow-control arrangement to remove some of the first component (the plasma) before the third component (comprising the platelets) is mixed with the first component. The system also preferably includes a plasma-volume determination sensor in communication with the controller; the plasma-volume determination sensor determines the volume of the first component in the rotor. The controller may thus remove a portion of the first component based on the determined volume of the first component.